diff --git a/backend/agent/llm/openai_provider.py b/backend/agent/llm/openai_provider.py
index 49f0538..139d840 100644
--- a/backend/agent/llm/openai_provider.py
+++ b/backend/agent/llm/openai_provider.py
@@ -540,6 +540,14 @@ class DeepSeekProvider(OpenAIProvider):
 
     _is_deepseek: bool = True
 
+    def supports_vision(self) -> bool:
+        """Return whether the selected DeepSeek model accepts image blocks."""
+        return self.model.lower() in {
+            "deepseek-flash",
+            "deepseek-v4-flash",
+            "deepseek-v4-flash-vision-exp",
+        }
+
     def __init__(self, model: str = "deepseek-flash", api_key: str | None = None, **kwargs) -> None:
         super().__init__(model=model, api_key=api_key, base_url="https://api.deepseek.com", **kwargs)
 
diff --git a/tests/test_deepseek_vision.py b/tests/test_deepseek_vision.py
new file mode 100644
index 0000000..0fc3d0b
--- /dev/null
+++ b/tests/test_deepseek_vision.py
@@ -0,0 +1,19 @@
+"""Vision capability checks for DeepSeek models."""
+
+from backend.agent.llm.openai_provider import DeepSeekProvider
+
+
+def test_deepseek_flash_supports_vision():
+    provider = DeepSeekProvider(model="deepseek-flash", api_key="test-key")
+    assert provider.supports_vision() is True
+
+
+def test_legacy_deepseek_flash_aliases_support_vision():
+    for model in ("deepseek-v4-flash", "deepseek-v4-flash-vision-exp"):
+        provider = DeepSeekProvider(model=model, api_key="test-key")
+        assert provider.supports_vision() is True
+
+
+def test_deepseek_pro_does_not_claim_vision_support():
+    provider = DeepSeekProvider(model="deepseek-v4-pro", api_key="test-key")
+    assert provider.supports_vision() is False